1. Field of the Invention
The present invention relates to a cleaning method carried out in a step of processing a semiconductor wafer of, for example, silicon.
2. Background Art
A semiconductor wafer (substrate) used in a semiconductor device is produced by processing an ingot block, which is grown by the Czochralski method or the floating zone method, into a mirror-surface-like thin plate. In processing steps thereof, mainly, (1) a slicing step of slicing the ingot block into wafers, (2) a beveling step of beveling an outer peripheral part of the sliced wafers, (3) a planarization step of planarizing the beveled wafers by using, for example, lapping or surface grinding, (4) an etching step for removing processing distortion of the planarized wafers, (5) a polishing step of polishing both surfaces or one surface of each of the etched wafers, (6) a thermal treatment step, an inspection step, various cleaning steps etc. are carried out.
Conventionally, in the polishing step of polishing one surface of a wafer, wax is applied onto one surface of the wafer that is to be polished, it is fixed to a turntable, and the other surface is polished. After this polishing step, in order to remove the wax adhering to the wafer and the particles adhered thereto during the process, cleaning using bases, etc. is carried out (see Japanese Unexamined Patent Application Publication No. 8-213356). In this method, the wax adhering to the wafer surface is sometimes removed in such a manner that it is exfoliated instead of being completely dissolved in a cleaning liquid, and there has been a possibility of residual wax remaining on the wafer after the cleaning.